I'll edit this post with some tips shortly, but the quick answer is SAVE YOUR STARDUST!
Edit:
Tips for new and early level GO players
1) Save your Stardust! The lower your player level, the lower the CP wild and hatched pokemon will have. As your level increases, you will find/hatch pokemon with higher CP. Don’t waste your stardust on early, low-level pokemon. You will constantly be catching and hatching stronger ones as you progress. Eggs stop increasing in CP at level 20 and wild pokemon stop increasing in CP at level 30. Don’t use a speck of Stardust until you’ve at least reached level 20+!
2) Eggs are better than wild Pokémon! If you know what Individual/Inherent Values (IVs) are, eggs typically have better IVs than wild pokemon. If you want the best pokemon for gyms, use your hatched pokemon for Power Ups and Evolving. Use the wild pokemon to fill your pokedex and collect candy/stardust, but don’t waste your stardust on them unless you know they have decent IVs. A higher CP doesn’t necessarily mean a pokemon is better than another. I explain IVs in more detail below.
3) Catch everything! Don’t be discouraged if you find a lot of Pidgey, Weedle, Caterpie, and Rattata. Those pokemon play an important role in leveling up. However, don’t waste a ton of your balls on any particular pokemon (unless you don’t have it in your pokedex or desperately need the candies). It’s not worth it to throw away 10 balls for 100 stardust and 4 candies. A pokemon with a really low catch rate will waste a lot of your balls and berries. It’s better to just run away from them.
4) Incubators are the best item for your money! If you put money into the game, Lucky Eggs and Incense are great items, but Incubators are much more important. I always try to have 9 eggs incubating at once. Hatching an egg gets you experience, stardust, a lot of candies, and stronger pokemon.
5) Lucky Eggs double your experience! The quickest way to gain experience and level your character is to evolve pokemon. Each evolution earns you 500 exp. When you have a Lucky Egg active, they become 1000 exp. All those Pidgey, Weedle and Rattata you catch are quick experience gains. Just activate a lucky egg and evolve away! You have 30 minutes to evolve as many pokemon as you can. Don’t waste your time transferring anything until you run out of pokemon to evolve or time on your lucky egg.
6) Use Incense for more Pokémon! Incense will attract random pokemon for 30 minutes. If you are moving at a decent pace, they will show up more frequently, but even sitting still with an incense can get you 1 about every 5 minutes.
7) There are tools to help you with the game.
https://thesilphroad.com/research is one of the best resources. Remember those IVs I mentioned? The Silph Road has a calculator to help you find out what your pokemon’s IVs are. They also have lists showing you how much experience you can earn for anything that earns you experience, what items you get when you level up, base stats for each pokemon, and information about attacks. It’s very useful for building Gym-ready pokemon.
Inherent Values
Pokemon have somewhat complex stats. CP is actually a combination of Attack and Defense, and they are both a combination of base stats and inherent values. Stamina or Health Points (HP) is also a combination of base stats and IVs. Base stats are the same for every pokemon of a species, meaning every Bulbasaur has the same base stats. IVs are different for every pokemon, meaning two Bulbasuar probably have different IVs.
Pokemon that hatch from eggs almost always have better IVs than wild pokemon. If you want to have the best pokemon for gym battles (and later 1-on-1 battles), then it’s worth it to evolve and power up your hatched pokemon even if it takes more Stardust to get them up to max. They will end up being stronger than a pokemon that was caught near max.
